Man page - sd_bus_message_unrefp(3)

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Manual

SD_BUS_MESSAGE_NEW

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
Errors
NOTES
HISTORY
SEE ALSO
NOTES

NAME

sd_bus_message_new, sd_bus_message_ref, sd_bus_message_unref, sd_bus_message_unrefp, SD_BUS_MESSAGE_METHOD_CALL, SD_BUS_MESSAGE_METHOD_RETURN, SD_BUS_MESSAGE_METHOD_ERROR, SD_BUS_MESSAGE_SIGNAL, sd_bus_message_get_bus - Create a new bus message object and create or destroy references to it

SYNOPSIS

#include <systemd/sd-bus.h>

enum {
SD_BUS_MESSAGE_METHOD_CALL ,
SD_BUS_MESSAGE_METHOD_RETURN ,
SD_BUS_MESSAGE_METHOD_ERROR ,
SD_BUS_MESSAGE_SIGNAL ,
};

	int sd_bus_message_new(sd_bus * bus , sd_bus_message m , uint8_t** type );
	sd_bus_message sd_bus_message_ref(sd_bus_message m );
	sd_bus_message sd_bus_message_unref(sd_bus_message m );
	void sd_bus_message_unrefp(sd_bus_message ** mp );
	sd_bus sd_bus_message_get_bus(sd_bus_message m );

DESCRIPTION

sd_bus_message_new() creates a new bus message object attached to the bus bus and returns it in the output parameter m . This object is reference-counted, and will be destroyed when all references are gone. Initially, the caller of this function owns the sole reference to the message object. Note that the message object holds a reference to the bus object, so the bus object will not be destroyed as long as the message exists.

Note: this is a low-level call. In most cases functions like sd_bus_message_new_method_call (3), sd_bus_message_new_method_error (3), sd_bus_message_new_method_return (3), and sd_bus_message_new_signal (3) that create a message of a certain type and initialize various fields are easier to use.

The type parameter specifies the type of the message. It must be one of SD_BUS_MESSAGE_METHOD_CALL — a method call, SD_BUS_MESSAGE_METHOD_RETURN — a method call reply, SD_BUS_MESSAGE_METHOD_ERROR — an error reply to a method call, SD_BUS_MESSAGE_SIGNAL — a broadcast message with no reply.

The flag to allow interactive authorization is initialized based on the current value set in the bus object, see sd_bus_set_allow_interactive_authorization (3). This may be changed using sd_bus_message_set_allow_interactive_authorization (3).

sd_bus_message_ref() increases the internal reference counter of m by one.

sd_bus_message_unref() decreases the internal reference counter of m by one. Once the reference count has dropped to zero, message object is destroyed and cannot be used anymore, so further calls to sd_bus_message_ref() or sd_bus_message_unref() are illegal.

sd_bus_message_unrefp() is similar to sd_bus_message_unref() but takes a pointer to a pointer to an sd_bus_message object. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute [1] . See sd_bus_new (3) for an example how to use the cleanup attribute.

sd_bus_message_ref() and sd_bus_message_unref() execute no operation if the passed in bus message object address is NULL . sd_bus_message_unrefp() will first dereference its argument, which must not be NULL , and will execute no operation if that is NULL .

sd_bus_message_get_bus() returns the bus object that message m is attached to.

RETURN VALUE

On success, sd_bus_message_new() returns 0 or a positive integer. On failure, it returns a negative errno-style error code.

sd_bus_message_ref() always returns the argument.

sd_bus_message_unref() always returns NULL .

sd_bus_message_get_bus() always returns the bus object.

Errors

Returned errors may indicate the following problems:

-EINVAL

Specified type is invalid.

-ENOTCONN

The bus parameter bus is NULL or the bus is not connected.

-ENOMEM

Memory allocation failed.

NOTES

Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config (1) file.

The code described here uses getenv (3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call setenv (3) from a parallel thread. It is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started.

HISTORY

sd_bus_message_new() , sd_bus_message_ref() , sd_bus_message_unref() , sd_bus_message_unrefp() , and sd_bus_message_get_bus() were added in version 240.

NOTES

Clean-up Variable Attribute

https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html

	int sd_bus_message_new(sd_bus * bus , sd_bus_message m , uint8_t** type );
	sd_bus_message sd_bus_message_ref(sd_bus_message m );
	sd_bus_message sd_bus_message_unref(sd_bus_message m );
	void sd_bus_message_unrefp(sd_bus_message ** mp );
	sd_bus sd_bus_message_get_bus(sd_bus_message m );